Answer
6/5 hours
Work Step by Step
Andrew completes in 2 hours alone (or gets 1/2 done in an hour)
Timothy completes in 3 hours alone (or gets 1/3 done in an hour)
$1/2 + 1/3 = 1/x$
$6(1/2 + 1/3 = 1/x)$
$3+ 2=6/x$
$5=6/x$
$5*x=6*x/x$
$5x=6$
$5x/5 = 6/5$
$x=6/5$